=/ pins a named value (a face) into the subject for the lines below it.

name=value optionally declares the type.

=/(a 3 (add a a)) is 6.

:* makes a tuple of many elements, nesting to the right.

:*(1 2 3) is [1 2 3].

irregular forms:

[a b c d] is :*(a b c d)

%= resolves a wing with some faces changed.

=/(a [x=1 y=2] a(x 9)) is [x=9 y=2].

irregular forms:

a(x 9) is %=(a x 9)

$(a b) restarts a loop with a changed to b